Abstract
This study was aimed at mapping the organization of the projections from the inferior olive (IO) to the ventral uvula in pigeons. The uvula is part of the vestibulocerebellum (VbC), which is involved in the processing of optic flow resulting from self-motion. As in other areas of the cerebellum, the uvula is organized into sagittal zones, which is apparent with respect to afferent inputs, the projection patterns of Purkinje cell (PC) efferents, the response properties of PCs and the expression of molecular markers such as zebrin II (ZII). ZII is heterogeneously expressed such that there are sagittal stripes of PCs with high ZII expression (ZII+), alternating with sagittal stripes of PCs with little to no ZII expression (ZII−). We have previously demonstrated that a ZII+/− stripe pair in the uvula constitutes a functional unit, insofar as the complex spike activity (CSA) of all PCs within a ZII+/− stripe pair respond to the same type of optic flow stimuli. In the present study we sought to map the climbing fiber (CF) inputs from the IO to the ZII+ and ZII− stripes in the uvula. We injected fluorescent Cholera Toxin B (CTB) of different colors (red and green) into ZII+ and ZII− bands of functional stripe pair. Injections in the ZII+ and ZII− bands resulted in retrograde labeling of spatially separate, but adjacent regions in the IO. Thus, although a ZII+/− stripe pair represents a functional unit in the pigeon uvula, CF inputs to the ZII+ and ZII− stripes of a unit arise from separate regions of the IO.
Highlights
Studies of the pigeon VbC have previously shown that a zebrin II (ZII)+/− stripe pair represents a functional unit insofar as the response of Purkinje cell (PC) complex spike activity (CSA) to optic flow stimuli is consistent within a ZII+/− stripe pair (Pakan et al, 2011; Graham and Wylie, 2012; see Figure 7E)
In the present study we showed that ZII+ and ZII− stripes within each functional unit in the uvula receive input from different, adjacent areas of the medial column of the inferior olive (mcIO)
The projection to the uvula arises from the lateral mcIO, which can be divided into six rostro-caudal regions
Summary
The cerebellum exhibits an organization defined by sagittal zones (Voogd and Bigaré, 1980), which is evident with respect to the distribution of afferent input from climbing fibers (CFs) and mossy fibers, the projection patterns of efferent Purkinje cell (PC) outputs, as well as from the response properties and synchronous firing of PCs (Llinas and Sasaki, 1989; De Zeeuw et al, 1994; Voogd and Glickstein, 1998; Wu et al, 1999; Ruigrok, 2003; Apps and Garwicz, 2005; Pakan and Wylie, 2008; Pakan et al, 2011, 2014; Graham and Wylie, 2012). Several studies have examined the relationship between ZII stripes and the aforementioned aspects of sagittal cerebellar organization (Gravel and Hawkes, 1990; Hawkes and Gravel, 1991; Matsushita et al, 1991; Akintunde and Eisenman, 1994; Chockkan and Hawkes, 1994; Ji and Hawkes, 1994; Voogd et al, 2003; Sugihara and Shinoda, 2004, 2007; Voogd and Ruigrok, 2004; Wadiche and Jahr, 2005; Gao et al, 2006; Pijpers et al, 2006; Sugihara and Quy, 2007; Sugihara et al, 2007; Ruigrok et al, 2008; Mostofi et al, 2010; Paukert et al, 2010; Sugihara, 2011; Zhou et al, 2014)
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